This invention relates to a marine engine exhaust system and more particularly to a marine wet exhaust system, which substantially reduces noise, fumes and odor and is mounted on the external portion of the marine vessel, called the transom, and is installed in such a manner as to be functional as a swin platform, a boarding, or a life saving device, facilitating access to the vessel from the waterline, and that provides a separate noise suppression chamber for each of a pair of marine engines in side by side orientation.
Present marine exhaust systems are subject to a variety of serious problems enumerated as follows:
a) designed to muffle sound, they are installed internally within the hull of the vessel. Any breakdown of the composition with which the mufflers are constructed, or breakdown of clamps due to vibration and corrosion, can lead to serious consequences by discharging dangerous fumes and water directly into the interior of the vessel. Because of this danger and the use of the interior space, many vessels using high performance diesel engines are sold without muffled exhaust systems installed;
b) the noise emissions from current marine engines have become intolerable, to an extent they provide a hazard to the operators and passengers of vessels, as well as the general public. Tests and studies show that marine diesel engines, at a crusing speed are operating at a sound level of more than 100 decibels within the immediate area of the vessel. According to the U.S. Department of Labor regulations, any noise level above 100 decibels is an impermissible noise beyond two hours of exposure. 115 decibels is the noise level of many vessels operated by diesel engines. If noise level exceeds 115 decibels, the permissible limit of exposure to that noise level is one-quarter of an hour, or less;
c) exhaust fumes and odor, particularly of diesel engines emitting through the transom exhaust are drawn back into the cockpit by turbulant air flow through what is known as the "stationwagon" effect, thereby endangering and inconveniencing the boat's occupants. Ingestion of toxic exhaust fumes by boat passengers is well documented as a serious threat to public health;
d) internal mufflers increase the heat level of the vessel. Heat levels on cruising vessels are extremely high, particularly with the high performance, turbo charged diesel engines now widely in use. Diesel engines operate most efficiently at temperatures approaching 200 degrees F. Turbo chargers add substantially to heat buildup in the engine room. Considerable heat is retained in the current internal muffler systems, as when the engines are stopped, the muffler retains approximately one third of its volume in water, which rests in the muffler casing and retains heat of high temperature, thereby taking longer for the interior to cool, adding to the discomfort of crew and passengers.
Previous attempts to reduce the noise of marine engines, particularly diesel engines, reducing the odor and fumes from the exhaust systems of the engines, and preventing their backflow into the open rear, or cockpit, of the boat, and reducing internal muffler ambient heat, have been largely unsuccessful. No attempt has been made to solve the most serious problem of all, namely the safety hazard of internal mufflers, by providing a muffler system that is mounted to the exterior of the hull of the vessel, which thereby eliminates any hazard of discharging water or exhaust gases into the interior of the hull, and at the same time projecting the exhaust at a distance farther aft of the vessel, directly into the water, thereby eliminating the flow of fumes and odor into the cockpit of the boat.
In U.S. Pat. No. 4,744,778 issued 5/17/88 to Porter, an external exhaust muffler bolts on the transom and also serves as a swim platform. This muffler is a chamber that extends from one side of the boat to the other with exhaust gas exit ports in line with exhaust gas entrance pipes so that there is no athwart or transverse flow pathway forced on the gas to provide an elongate flow path through the muffler chamber for efficient silencing and gas scrubbing. And gas is not directed to exhaust along the center line. No special provisions are made for changing the exhaust vertical level between slow and planing speeds. Furthermore, the chamber of Porter makes no provision for the large mass of water that will accumulate in the chamber from both the surrounding water and the cooling water mixed with the exhaust. When running in reverse, extensions of the type shown by Porter may tend to dig into the sea and cause water to flow into the boat as well as into the chamber and the engine exhaust pipes causing serious problems.
The exhaust system disclosed in a patent application that will be U.S. Pat. No. 4,977,977 works very effectively at high speeds where the exhaust is pulled through the lowermost, centerline outlets, but at low speeds the centerline uppermost exhaust ports do allow exhaust gases to come in over the transom under some conditions, which is undesirable.
Accordingly, there is a need for a simple, durable, inexpensive, but highly effective, marine exhaust system, which prevents and avoids internal breakdown, reduces substantially noise levels of the marine engines, reduces internal heat levels, provides a life saving and recreational attachment to the vessel, without interfering with engine performance, and prevents exhaust gas from coming in over the transom at both low and high speeds.